9781422284995

“This is the work that the engines do to propel us forward,” she continued. “There must be a force, then, to counterbalance the lift I was talking about,” said Mei. “Of course there is. That’s gravity !” Hayato said. Mei looked out the window. “That’s a lot of forces that all have to work together to get us up in the air and on our way home.”

Sir Isaac Newton and Flight Sir Isaac Newton died nearly 150 years before Orville and Wilbur Wright built the first working airplane in 1903. But it was Newton’s laws of motion that explained how and why flight is possible. His laws said the following:

• An object that is at rest will remain at rest until an outside force acts upon it. If an ob- ject is in motion, then it will stay in motion and not change direction unless it is acted upon by an outside force. • The harder an object is pushed, the far- ther and faster it will move. • If an object is pushed in one direction, there is resistance on that object working in the opposite direction. These three laws of motion led to the understanding that the four forces of lift, drag, gravity, and thrust all must act togeth- er to make flight possible.

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